A look inside API Recommended Practice 1175, part 4

Analysis of a Leak Indication

Certain leak indications may require an immediate shutdown of the pipeline while other indications may dictate that the Pipeline Controller analyze the current pipeline operation or escalate the investigation. The magnitude of the leak and the level of risk involved may be the key factors in the decision.

Leak Indications Requiring Immediate Shutdown Response

Alarms that are clear and credible such as a clearly defined signature, or where a Pipeline Controller believes the leak indication or the indication is highly reliable.

Some operators may have the policy to shut down whatever the alarm.

Leak Indications Allowing Additional Analysis before Shutdown

An operator may have a second category of alarm response where alarms require timely investigation and preparation for shutdown. These instances include, among others, alarms not supported by the hydraulic conditions, loss of communications, alarms that coincide with start-up/shutdown or rate changes, and a number of others.

The goal is to improve learning, to increase the number of clear and credible alarms and reduce uncertain alarms and overall improvement. Another objective to see if threshold changes are required.

The pipeline operator performs both short-term periodic reviews (daily, weekly, or monthly) of alarms and long-term periodic review (for example, a five-year cycle) of alarms. The evaluation may indicate what to do strategically in managing the types of alarms. This information then feeds into improvement planning.

Review may result in recommendations to improve the alarm response or repair instrument or equipment failures (e.g. PLC failures) etc.

Long-term Periodic Review

The time between the long term reviews should not exceed five years. The review should assess the alarm performance and thresholds from the perspective of sensitivity and reliability with respect to the KPIs and performance metrics.

Actual Leaks

The LDS response should be analyzed and documented. General classifications for review of actual leaks may within scope (the leak was big enough to be detected and was or was not detected) or out of scope (too small to be detected). Report the lessons learned. If the LDS failed to detect a leak that is within its scope of the LDS, investigate and identify corrective actions.